Phil, do yourself a big favour and stop your silly antics you have already been BANNED from one dz that I jump at because you were a danger to yourself. You cannot call it a canopy, it's a very big kite and what happened to the orange kite you built nobody in there right mind will ever let you jump out of a plane with it and even a rigger tried giving you advise which you went mad at them because they was not telling you what you wanted to hear,please stop before you really hurt yourself or others around you and from what i remember of you you dont no how to say no, its not you and if you carry on doing this project which you will you are going to hurt yourself really bad or others around you and for god sake WEAR A BLOODY LID and phil im not having a moan or a dig I'm only looking out for your safety and your life and fair play you have built somthing not many others will ever have a clue to do including myself

Here's a question for all you knowledgeable people out there. Is a single row of zigzag stitching an acceptable way to secure a fingertrap on a suspension line? I could swear I've seen it on some older flight concepts designs. I would take a picture of what it looks like, but my camera can't focus on it.

I've seen older canopies use a few inches of loose zigzag with a couple of stitches worth of over-stitch at each end.

My favorite way to sew lines without a bartacker, though, is a technique that I think hookitt posted a few year back. Sew a pass of zigzag, then pick the foot up and move the line back to the starting point and sew a second pass right over the top. The loose thread should be trapped in the second pass. It works well in a lot of places that you would normally use a bartack. For line work, make sure that the stitch is narrow enough and centered so that it goes through both lines in the fingertrap. If it's a line on a canopy I set the width and SPI to match the factory bartacks. 3/4" long and 42 total stitches is a good starting point if you don't have anything to compare to.

I think the sewing is over rated in it's importance. Remember that as long as you have a decent length finger trap most of the strength is in the finger trap it self. Length varies by line and weave but 4 inches is a good round number. The stitching is more then any thing else to prevent it's slipping before it has good load on it. The truth is a little more complicated. Some joints are more problimatic then others. As an example a casscade really likes to have a little tension on the A line to help with the strength of the B line junction. So we sew things. Don't over think it. You could almost get by jumping the canopy with out sewing any thing. The line attachments that I described earlier as an example and you'll want to to play with trim so make those finger traps long or leave tailes hanging out. Long finger traps shrink line. Some times just finger trapping a section of line in to a suspension line is an easy way to treak the trim on a canopy.

As to sewing. We've done every thing over the years and it's all worked. With just a little home machine and a test bed canopy I'd just do a relitively lose zigzag say an inch and a half to two inches long. Make it lose enough that you will be able to take it out if you have to. Glide path did some thing like this for years on dacron line. Remember, Test bed.

Best way to sew it is to make a "Line Jig" Take two peaces of webbing, weight depends on line say type eight for 825 spectra, About 5 inch long. Spread them to the width of the finger trapped line. Put two peaces of type four tape across the ends. sew them across the ends to keep the spaceing. You have a window. Place the line on the machine. Place the jig on the machine on top of it webbing down so it stadels the line. It will hold the line centered as you sew it and lit you feed it much more smoothly. The jig and line all feed through the machine as one. Slide the line out , put a new one in and repeat. Once you've done that set. I like to chain link the lines leaving a gap and then starting again below the cascade so that all the sew points are there togather. Move on to the next group. You can count and inspect them all togather right there. Remember, if you do a non cascaded line set for now you can do all the lines sepperatly and then larks head or sheet shank the lines onto the canopy rather then sew them with the whole pile of canopy in your lap. Your going to be fuicking with this so you don't need a lot of complexity slowing down the evelutionary process. And when you're pre planning you're trim changes that you're going to make in the field when testing. Remember It's easier to make lines shorter then longer. Pre mark all your trim changes with diffrent color sharpies. Buy a box with a whole rainbow.

Basically I'm saying that I'd build my self a set of non cascaded "test lines" pre marked at various trims. Left unsewed at eather the top or bottom. Mark them with various colors of sharpies and just chang them with a little wire fid. I'd take this out and tye it down at the risers or a little longer. One straight peace of webbing or line at the base will let you make a dirrect measurement of glide angle. I'd measure glide and play with stability at a viriety of trims and then go back and feed that back into my model. So at that point doing the math you've got a spread of glide angles at various AoA for the canopy. As go back to computer you can incororate that into you're next plane form to optimise you're next panel set. Then the cycle repeats till you've got some thing that a nice smooth wing with good lift across the canopy, about the right trim you want, and some idea of it's stability. Play with you're break as well. For each of those trims measure three or four break setting down to half breaks. As you play more with it out of the airplane You'll be able to start equateing that data to how it pitches and setts up. Withen two possable three generations you should have something that you're willing to at least test jump if not yet ready to land. Don't go and do some thing silly like comit your self to landing a new canopy till you think you're happy with how it pitches and it's stability.

the late Freeman Frame from FWF Industries( they used to make the original braided dacron line for para flite) always said the rule of thumb was 20 times the diameter for trapping. the ONLY thing stitching does is keep the trapped portion of line from creeping back out when there is no load.the stitching does not add any structural strength.

the late Freeman Frame from FWF Industries( they used to make the original braided dacron line for para flite) always said the rule of thumb was 20 times the diameter for trapping. the ONLY thing stitching does is keep the trapped portion of line from creeping back out when there is no load.the stitching does not add any structural strength.

A guy I worked with quite possibly inspired the testing to find that 'rule of thumb'. For most lines it's fine, but there are some out there that will slide right out with that short of a finger trap. Mostly a non-issue on the sport side of things (with the lines we use) but it CAN vary.

Lee, You gave the OP a flaming because he did not wear a helmet and then you turn around and give out bullshit info!

WTF!!!

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You could almost get by jumping the canopy with out sewing any thing.

This is a good example.

We do not need someone out there to read this and actually go try it because the finger trap can work loose during packing and deployment if not sewn.

In reply to:

Best way to sew it is to make a "Line Jig" Take two peaces of webbing, weight depends on line say type eight for 825 spectra,

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825 Spectra only exsists in PD's world. It is a number they used to identify coated 725 line verus the un-coated 725 line.

In other words, there is no such animal..... Just look at the identification label on the spool.

Glide path did some thing like this for years on dacron line.

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They did it on Spectra also. Flight Concepts ( New Name) still uses that method. It is done with a bartack machine BTW....

Basically I'm saying that I'd build my self a set of non cascaded "test lines" pre marked at various trims. Left unsewed at eather the top or bottom. ....

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This is the final clue that you do not have one!

There are major differences in a casscaded line set and a non-casscaded one.

Casscaded line set uses line length AND the intersects of the B and D lines to set up the CG of the canopy. Non-casscaded line sets use just total line length to achieve the same. Therefore, the dimensions should be different for each.

Playing with this stuff is dangerous and should be treated as such.

The last thing we need is someone to go in because of mis-information and there is a ton of it in this thread.

That's why I posted a while back about line trims on the Optimum reserve. I ended up ringing PD, and the reason they don't give out line cascade points is to stop people like me from manufacturing duplicate line sets. Line trim charts are to check your canopy is in trim only. The way I have created my line lengths is to copy the total lengths from a known canopy, and then put cascades halfway up the longer line. I then cut these out of cheap, strong, nylon cord and tie them in knots as a temporary line set.

Sewing finger traps at line attachments. I told the whole story before but I don't have the patintce to re type it. I'll just say that I've got hundreds of jumps on canopies like this as we test jumped them. It works fine. If you are refering to cascades, yes you note that I mentioned that they were dependent on the main line tension to hold them.

825, Yes that's correct. I do tend to use the terms interchangable depending on who I'm talking to. PD has almost become a standard in the industry to the point that there nominclature has become almost a standard. It's the easyest way to comunicate some times. I also ask for a klenex when I need to blow my nose not a faceal tissue. Sue me. I don't think this guy has descovered CSR yet. If he had I'd have called it 9512-725. You know what that means but he wont.

Red has a very nice bartacker... now. That wasn't allways the case. Or at least furries old one must have been defective because it changed length randomly from line to line on a line set. In fact I beleve I remember when they baught it. I remember they were kind of excited. We all have nice toys now, the industry has come a long way. but asking the boy to buy a $5000 pattern tacker is probable a bit much. I stand by the process I described. If the boy wont's to sew line sets on his mothers home maching that's his best bet.

Cascades. I'm very aware of the diffrences between a cascaded and and uncascaded line set. Based on your commit I think I have a better grasp of the math then you. That is in fact why I recomended that he beguin by playing with a non cascaded line set. It's actually much simpiler.

What you are trying to say is... half right. It's not about the CG of the canopy. What it's actually about is the pressure distrobution across the airfoil. If you look at the coeficent of pressure across the airfoil you can basicly look at the lift distrobution along the cord line. This can be set of in a statics model if you were so inclined but mostly people do it by rule of thumb. The bitch of it is that the Cp changes across the airfoil as you change angle of attack. This can change the load on the cascade and bend and destort the airfoil. Cascades are actually a bad thing. We really shouldn't have them in our canopies but it's a compermise betweed drag and a lot of spigetti and the stability of the wing. That's what we're really talking about. As you go from a non cascaded line set to one with cascades yes, the lengths do change. As an example when you cascade a line set the B line is almost the same but the A actually gets a bit longer. The B actually has a bit more load on it in flight and pulls the cascade to the rear. The down side of this is that when the canopy comes to a higher angle of attack, eg. durring flare, the pressure distrobution changes and the load on the A line increases and it actually tips the nose up by distorting the airfoil as the cascade shifts. The CG does not chang relitive to the 1/4 cord point of the canopy the airfoil just bends in a bit of a z. It's suttle but there. It's enough that you can actually improve the performance of a canopy at higher angles of attack by removing the cascades on the A/B lines. Yes, this means tweeking the trim in the revers of what I described before. A lines get shorter. But some times it can be worth it to do this at least on say the center part of the canopy. Again it's a compromise.

Is that a bit clearer? Would you like me to send you a presure diagram? I was trying to avoid confusing the poor guy. So Like I said. Maybe he should just start out with a nice non cascaded line set. Nice and simple. Easy to adjust. Easy to play with.

If I've been unclear I'l be happy to explane further. If you want a debate of design I'm down for it. But if you want to get it on you better bring the math cause I was busting the curve in partial courses as a freshman. By the end of the semester it was down to to the grad students and me, and I think one senior was still hanging in there. Can't spell for shit but I could always do the math.

Sewing finger traps at line attachments. I told the whole story before but I don't have the patintce to re type it. I'll just say that I've got hundreds of jumps on canopies like this as we test jumped them. It works fine. If you are refering to cascades, yes you note that I mentioned that they were dependent on the main line tension to hold them.

My whole point is that you do not give out bad advice regarding not sewing fingertraps..period.

It is straight up,bad advice and dangerous.

If someone is too lazy to spend 20-30 seconds to rip out a simple bartack or other sewn method, then he/or she needs to do something else in this world IMHO!

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825, Yes that's correct. I do tend to use the terms interchangable depending on who I'm talking to. PD has almost become a standard in the industry to the point that there nominclature has become almost a standard.

They are not the majority. The other few dozen manufacturers and the hundreds of riggers out in the field are the majority. Most tend to use the tensile strength name that the braiders use. This eliminates confusion amongst the majority BTW.

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Red has a very nice bartacker... now. That wasn't allways the case. Or at least furries old one must have been defective because it changed length randomly from line to line on a line set. In fact I beleve I remember when they baught it. I remember they were kind of excited. We all have nice toys now, the industry has come a long way. but asking the boy to buy a $5000 pattern tacker is probable a bit much. I stand by the process I described. If the boy wont's to sew line sets on his mothers home maching that's his best bet.

Actually in earlier years, they just used a Singer 20U....

Then progressed to bartackers, and finally to programable bartackers. Cascades. I'm very aware of the diffrences between a cascaded and and uncascaded line set. Based on your commit I think I have a better grasp of the math then you. That is in fact why I recomended that he beguin by playing with a non cascaded line set. It's actually much simpiler.

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Why would you venture to think that you have a better grasp on this?

I have built literally thousands of line sets over the years and also for virtually every canopy out there in use today.

What's your resume or experience in line manufacturing and canopy design?

I also doubt very seriously that you have a higher concept of math, but it could be possible.

And remember, I have Excel and CAD programs here too!

What you are trying to say is... half right. It's not about the CG of the canopy. What it's actually about is the pressure distrobution across the airfoil. If you look at the coeficent of pressure across the airfoil you can basicly look at the lift distrobution along the cord line. This can be set of in a statics model if you were so inclined but mostly people do it by rule of thumb. The bitch of it is that the Cp changes across the airfoil as you change angle of attack. This can change the load on the cascade and bend and destort the airfoil. Cascades are actually a bad thing. We really shouldn't have them in our canopies but it's a compermise betweed drag and a lot of spigetti and the stability of the wing. That's what we're really talking about. As you go from a non cascaded line set to one with cascades yes, the lengths do change. As an example when you cascade a line set the B line is almost the same but the A actually gets a bit longer. The B actually has a bit more load on it in flight and pulls the cascade to the rear. The down side of this is that when the canopy comes to a higher angle of attack, eg. durring flare, the pressure distrobution changes and the load on the A line increases and it actually tips the nose up by distorting the airfoil as the cascade shifts. The CG does not chang relitive to the 1/4 cord point of the canopy the airfoil just bends in a bit of a z. It's suttle but there. It's enough that you can actually improve the performance of a canopy at higher angles of attack by removing the cascades on the A/B lines. Yes, this means tweeking the trim in the revers of what I described before. A lines get shorter. But some times it can be worth it to do this at least on say the center part of the canopy. Again it's a compromise.

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No, it was all right!

The CG can be altered by the line dimensions (casscaded or non-casscaded). That is fact.

Yes, changing the CG changes the pressurization of the canopy, so it still boils down to where that weight is hanging under the wing...

Is that a bit clearer? Would you like me to send you a presure diagram? I was trying to avoid confusing the poor guy. So Like I said. Maybe he should just start out with a nice non cascaded line set. Nice and simple. Easy to adjust. Easy to play with.

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Lee, I am already ahead of you in that game. Like I said, I have been dealing with lines, canopy trim and trim specs for years. I think I am past a primer in canopy design.

I also think the OP is past that as he is already flying his canopy.

If I've been unclear I'l be happy to explane further. If you want a debate of design I'm down for it. But if you want to get it on you better bring the math cause I was busting the curve in partial courses as a freshman. By the end of the semester it was down to to the grad students and me, and I think one senior was still hanging in there. Can't spell for shit but I could always do the math.

... I too excelled in math at a very early age. ...and also, actually went to school believe it or not!

The CG is going to hang underneath the canopy at a point dependent on it's AC and moment. Glide and AoA chase each other to stabillity. Yes we control where that settles through the line set. None of that is under debate. Maybe my first attempt at the post would have been clearer but the machine ate it.

The question was how cascades effect the canopy. And that is not through a grose change in the CG but through the abbility of the cascade to float forwards or back dependent on it's loading. That is where the trim change, change in the line set, it's really to maintain the same trim, comes from between the two types of line sets. Unforenently it can only be optimised for one mode of flight and will lead to distortion in others. As to how big a problem this is depends on the angle of the cascade and how critical the wing is. He has mentioned stabillity in deep breaks and it is noticable even in conservitive canopies on deep break approaches. In fact it was one of the things people would tweek on older acceracy canopies.

This has degenerated into a little bit of a debate between us. Part of it I think is symantics. Writeing is not my best means of comunication and I'm not sure you're always understanding me. This is to some degree my failing.

I think that although the things you say are not wholley wrong I beleave you are missing some of the suttaller issues as to how and why these things work. This is a good example. You're statement that the trim changes between a cascaded and non cascaded line set is corect but I take issue whith your statement as to why this is.

I'm not trying to give you lessens although I will debate points with you. I was a little verbose not so much because I felt that it was nessasary for you but in hopes that the guy in question would more clearly follow what we were arguing over.

As to how long the loop... good question. I think there are a couple of issues. One argument says that the lines should not be able to slip over each other. If it sets on top of another line the bump of the lower line can be a sharp enough radious to cut the lin on top of it under load. Note that this is some thing you see in really heavy test drops, cargo weights. On the other hand if the loop is to tight around the shaft of the link it can pull apart hard enough at the Y to tear the mouth of the opening causing the line to fail at the junction rather then at the end of the finger trap which is the normal failure point. I've seen that too when you start to get above about 1,500 lb. I've also hear it said that the loop should not allow the line to slip over the barrel of the rapid link assuming you are useing one and size it based on that. You'll probable wind up with a 1/2 to 3/4 inch loop depending on line and link. and of course cut the line off at as shalow of an angle as the weave will permit. Heavier lines you actually cut yarns at intervals along the line to smothly form a taper. Like the heavier line/"rope" of a sail boat. You can actually do this with braided core line by finger traping the core and the sheath into each other and the that junction actoally winds up inside the line above the loop. That's cool but I don't think I can explane it over e-mail. I only learned to do that a few years ago when I started sailing. I'd always wondered how they did that. I was jumping up and down with excitement when I finally learned how it worked. Other then that it looks fine. Sewing looks good. Don't feel you have to sew right up to the junction.

I took on a bit of Riggerlee's advice and thought about the shape of the inflated canopy. What I have done for my kites in the past is a rectangle for the bottom skin, and a rectangle for the top skin. This works well enough, but it is not the ideal solution. I didn't really understand what RiggerLee was on about, and I couldn't use the excel tables because I'm using a proprietary airfoil, so I came up with my own. Basically, the bottom skin is still rectangular, but the top skin has additional width which is proportional to its height obove the bottom skin. This meant I had the take my smooth rib design and make it into a series of points. The good news is that should make matching up the parts for sewing later easier.

I'm thinking about fabricating a 110 sqft model to see how well this works.

That's pritty much it. It look just about right. The question of whether the bottom skin is rectangular or not is a question of what line in space you rotate the rib around to create the pannel. In this case and in the example I sent you that line happened to be paralel to the bottom skin of the canopy. That does not nessasarily have to be the case. If you rotate the airfoil you can rotate it around to create a constant angle of attack around the line of rotation. Damn I'm not saying that very well. As you have it there if the canopy flies along the direction of the line you are rotating the canopy around it will be at "zero" angle of attack all across the span. Not to say that it's not makeing lift, keep in mind where your zero lift line, seperit angle, is. So if you want it to fly at a greater or lesser angle then the bottom skin will not nessasarily be a rectangle. I am so not explaining this well. Dork around with it a bit changing the angle of attack. It's ment to rotate the airfoil around a stream line to create the panel shapes. Now what it doesn't do is to tell you any thing about it's performance at that angle of attack and where it will want to fly. The line lengths it gives out are just an after thought based purely on an "assumed glide angle that you enter. It's ment as nothing but a starting point. From which to do a first cut. Once you play with a number of trims and phisically measure the glide that it wants to fly at and from there the AoA of the airfoil you can then feed those numbers back into the program to improve you're panel shape for where you are really flying.

Does that make any sence at all? In any case what you have there is exactly what you have created. If you feed your corordonents into the basic airfoil shape at the very begining it should proliferate through out the document. It will actually let you smush the airfoil around moveing the leading edge points for the top and bottom skin to change the nose cut. You can move the thirty percent point on the airfoil forwards and back to control the location of the greatest thickness/camber of the airfoil. and you can change the total thickness. The other nice thing is it will do patern shapes for an eliptic canopy. I just put in a simple rule to allow you to easily change the taper but you could easily set the rib lengths manualy to what ever you want. It rotates the 25% cord point so there will be more taper on the trailing edge then the leading. It basically unrolls the panel off of the wing as a section of cone. It's broken into a bunch of triangler panels to spread it out flat into the pattern it gives you. All in all it's a good bit for a couple of nights fucking off.

I'd almost have to walk you through it. You might have to give me a call. I don't supose you have skype on your computer?

Like the other poster said, you might want to make them a bit smaller. How much smaller is a question of whether to make them slightly bigger than the threads on Maillon Rapide links (redundant, I know), or slightly bigger than the hexagonal barrel. The goal is to make the loops just big enough that you can slide them onto links without scratching them across threads. For quality control, find a pencil, or pen of rod that is slightly bigger than your threads. Pull the loops tight around your rod and sew. Then you will have consistent loop sizes.

While we are on the subject of quality control ... try making your bar-tacks slightly narrower, so that all the stitches catch the inner line.

I actually had to go to a paper manufactorer. There was one there in Dallas. I went in and explaned what I wanted. I had to finger fuck a few samples but they had exactly what I needed right there in the ware house. It wasn't even that exspencive. honestly the hardest part of the whole thing was putting the roll in the car. It out wieghed me by a good margin. Paper is HEAVY. But I've got a life time supply of patern paper.

You're looking for some thing about the weight of poster board. Mine is manilla in color. Sorry Wish I could tell you more but that was years ago. Tryed to get what I wanted else where in smaller quantities but no joy. Poor me I had to buy a whole roll for half the total cost of buying a smaller quantity.

As for the stops, Get some large finder washers. There's actually a good bit of force on them. Don't skimp perticuarly on how you sew them to the lines. The stabalizers tend to get tears around the stops. Or at least that's where they start. I'm not sure it's extreame stress so much as the fact that the fabric is always at a weird bias there. You get weird little tears. So don't be afraid to put some tape there running along diffrent angles to help protect it from weird loads. See how PD runs a tape across the top of the stops or a vertical tape.

I had a very productive conversation with J Wragg; he answered a lot of my questions and make me think about a few things that hadn't crossed my mind. I may have hit a snag as far as testing goes, see the BPA ops manual:

"Parachutes may only be used if they are manufactured for Sport Parachutists or Military Parachutists, by recognised parachute equipment manufacturers or riggers with the necessary qualifications."

However: "BPA ‘A’ Licence parachutists and above may perform cutaways (at a club PLA/DZ) with a cutaway `rig’ designed for the purpose, provided they have CCI permission and have been thoroughly drilled in the cutaway procedures."

So technically I could do a cutaway jump on my A licence, but I'd have to leave the test jumping for someone else for now.